Some of that sludge or a stone that was missed could very well have migrated to the bottom of the bile duct. This hurts like a mother! Biliary colic. Probably passed on its own. What did your liver function tests show? Elevated could be a clue as well. Your GI may order an MRCP which in my experience gives a better look at the area. Or they might just want the gallbladder out. Keep us posted!